The Impact of Incarceration and Substance Abuse on HIV-Infected Veterans Abstract: The United States has the highest rate of incarceration worldwide, such that more than 13 million individuals have been incarcerated in jail or prison. One half of all prisoners meet criteria for drug abuse or dependence and one in seven individuals infected with HIV is incarcerated each year. Compared with HIV- infected individuals never incarcerated, current and former inmates have worse HIV disease control and increased mortality, although the specific mechanisms for this are unknown. This worsening of HIV-infected patients' disease upon release to the community is associated with relapse to substance abuse and worse adherence to antiretroviral therapy. However, the majority of HIV-infected individuals released from incarceration do not receive substance abuse treatment when needed, and the independent impact of substance abuse on poor health outcomes is unclear. This makes it difficult to design interventions that provide needed substance abuse treatment and improve HIV outcomes. An improved understanding of the impact of incarceration on HIV disease control among individuals with drug and unhealthy alcohol use and the effects of moving between multiple health care systems is necessary for improving the health of individuals with HIV and substance abuse. The proposed aims for this application are: (1) to determine the independent impact of incarceration on HIV disease control in veterans and (2) to identify possible substance abuse-related mechanisms by which incarceration affects HIV disease control. We hypothesize that there is a dose dependent relationship between frequency of incarceration and worse HIV outcomes and that lack of substance abuse treatment, among individuals who report drug and unhealthy alcohol use, mediates this association. To empirically test these hypotheses, we will conduct general estimating equation and latent growth models on data from the Veterans Aging Cohort Study (VACS), an ongoing longitudinal, multisite cohort study of 2902 HIV-infected veterans, to study the impact of incarceration on long term HIV outcomes and potential mediators of observed observations. The Veterans Health Administration is an ideal setting to study the impact of incarceration on HIV disease control, as it is the single largest health care provider of HIV- infected individuals in the U.S. and is largey a closed system of care. Also, because VACS includes extensive measures of potential substance abuse-related mechanisms, we will be able to thoroughly examine the independent impact of incarceration on HIV disease control and identify mutable substance abuse-related mechanisms. These analyses are a necessary first step to identifying such mediators, thus allowing us to efficiently target future intervention studies to improve the health of HIV-infected veterans, a unique and understudied patient population, and reduce the spread of HIV disease.